COE Pickled metal prep?

I used 16 g sheet metal for my bed . It seams to have a black coating on it . Do I have to remove it or can it be treated so I can prime . Striping will take 3/4 days . I used rust blast ,then this stripper . Panels are so big I would be scared to blast them . Blue

 

That is mill scale from hot rolled steel. Not pickled steel. Cold rolled steel is normally used when a high quality finish is required. You can sandblast it off if you need a show finish. If you had pickled steel, the pickling process would have removed that black mill scale with acid. Then finished with oil to preserve the metal.

 

To answer your question, I would remove the black scale. It is actually a form of rust called iron oxide.

 

Tony , this metal is very smoth and doesn't flake when formed or bent and drills like cold roll . If it's mill scale how would you remove , thanks for the help . Blue

 

It looks like you already removed half of it. I would remove all of the black mill scale on the outside of the bed. Just sand it off with co**** paper like you've been doing. Go over the inside bed surface with a DA and 80 grit paper.

In the future, think about using cold rolled steel instead. Much nicer surface finish to start with.

 

Will do , thank you , Blue

 

Yup, sand it off! To be doubly sure go to your local farm supply store, and buy milker pipeline cleaner (Don't know if you have enough dairy in Texas) and wetly wipe the steel down. if possible get the surface horizontal, get it wet and cover with plastic to stop evaporation. when done removing oxidation, rinse with water and give it a final wipedown with a rag dampened with the acid and let dry. A white powder will appear, wipe that off with a dry towel, and do your normal grease/wax prep and epoxy or acid etch primer. Milker pipeline cleaner/milkstone remover is about 50% phosphoric acid and 50% water wetter

 

Acid removes it easily, but it is dangerous to use. I cleaned some parts with driveway cleaner acid. You definitely need to protect your eyes, lungs and other precious body parts. You could use towels dunked in the acid and set them on the panel. After 10 minutes, the black stuff will almost wipe off. Do it on your driveway and you get a two for one...white spots on the drive. Bill would tell you to use mol***es...

 

How about some of that kc BBQ sauce .lol it sure was good , just ordered a case off web , thanks KS

 

That BBQ sauce won't remove the black coating, but it will make your bathroom scale advance. Hmmm, I wonder if it will stop all my engine leaks?

 

BTW, the acid I suggested is the main flavoring ingredient in Coca-Cola, this is why Coke will dissolve the rust off a nail! You can literally drink diluted phosphoric acid!
Drive-way cleaning acid is probably muriatic (hydrochloric and sulfuric mix) which will leach out of a sealed jug and rust everything in your garage!

 

You are right...I kept the acid outside just because of that exact rust potencial. I wonder if driveway acid was used in "new coke"

 

I have heard of the pool chemical "PH reducer" used to remove the mill scale. It is fairly safe and cheap.

 

I will try some of the acids . I did buy a pressured sand blaster . Holds 2 bags of sand and I will try it out this week and see if my 5 horse compressor will push it .

 

It might help to connect a second air tank to get some stored air volume and wait in-between filling up cycles. I never seem to have much luck blasting at home, but part of that is the high humidity.

 

Got the blaster today and put a bag of sand three it . Compressor kept up pretty good but next time I will put my 3 horse in line for better air reserve . Going out of town next week to get some sand and was thinking of fine sand . Is this the right grit ? The supply house sells it by the skid ,33 bags . Only have to go 200 miles to get it . I figure it will take all of that to do ,or get a good start on my truck .

 

I blast in a clean area and lay a large tarp down, then I can catch most of the sand and I run it through a fine metal windows screen and reuse it.

 

KS has the right idea, screen and reuse your sand! I've found that the finer the sand, the better it is at paint and rust removal. Smaller grains carry less energy, so you get less warpage on sheet metal and the smaller grains get in the little rust pockets better, so you get a cleaner job.

 

and wear head protection...sand will get in your eyes, ears, and everywhere. I wore a hat, a welding hood with clear lens, gloves, and a full ****on up shirt. The worst is the eyes. If you get sand in your hair, be careful it does not fall into your eyes later.